This project is designed to increase knowledge of the epidemiology of human Chlamydia trachomatis infections. The etiological role of these organisms in trachoma, non gonorrheal urethritis (of the male), inclusion conjunctivitis of the newborn, and pneumonitis of infancy has been established and much has been learned about the epidemiology of C. trachomatis infections of the eye, the genital tract, and newborns in both trachoma endemic and nonendemic areas of the world. Evidence regarding the disease significance of C. trachomatis infections of the female genital tract (cervicitis, salpingitis, peritonitis and perihepatitis) has been accumulating and studies of these infections are proposed. Although no etiological significance has yet been demonstrated, the organisms have been isolated from the middle ear, pharynx and the rectum. We have serologic epidemiological data from U.S. population groups strongly suggesting that these organisms cause more frequent infection than can be accounted for by known eye and genital tract disease. Our serological data suggests that C. trachomatis is etiologically associated with pneumonia of children after infancy and in adults. A series of studies of the role of C. trachomatis in pneumonia and acute lower respiratory disease are proposed. In addition we plan to utilize our unique specific serological test (micro immunofluorescence) for both serum and local secretions in preliminary studies of various disease syndromes potentially associated with C. trachomatis (acute respiratory disease, chronic obstructive pulmonary diseases, sinusitis, otitis, ideopathic inflammation of the bowel) to identify targets for some specific etiological and epidemiological studies. Patients with compromised pulmonary (e.g. cystic fibrosis) or immunological systems will be studied to determine the potential role of C. trachomatis in their disease process. Also, couples with infertility problems will be similarly investigated.